JP2003142904A - Transmission line - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transmission line whose characteristic deterioration due to reflection of a signal of high frequency, crosstalk, etc., is suppressed. SOLUTION: A center conductor 2 is formed on the top surface of a dielectric substrate 1 and top-surface ground conductors 3 are formed at both sides of the center conductor; and a reverse-surface ground conductor 5 is formed on the reverse surface of the dielectric substrate 1 and a conductor wall 4 is formed which penetrates the dielectric substrate 1 between the top and reverse side, extends in the extension direction of the center conductor 2, and electrically connects the top-surface ground conductors 3 and reverse-surface conductor 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission line that constitutes a high frequency circuit.

[0002]

2. Description of the Related Art FIG. 7 is a diagram showing a configuration example of a coplanar guide transmission line that has been conventionally used as a high-frequency transmission line. (A) is a plan view, (b) is a line bb of (a). FIG. In FIG. 7, 1 is a dielectric substrate, 2 is a center conductor as a signal line formed on the surface of the dielectric substrate 1, 3 is a surface ground conductor formed on both sides of the center conductor 2, and 5 is a dielectric substrate. A back surface ground conductor formed on the back surface of 1 and 6 are via holes for electrically connecting the front surface ground conductor 3 and the back surface ground conductor 5. Generally, at high frequencies, in the coplanar guide transmission line, a higher-order propagation mode is generated between the ground conductors 3 and 5 on the front surface and the back surface of the dielectric substrate 1, and the characteristics of the transmission line deteriorate.

Therefore, in the conventional coplanar guide transmission line shown in FIG. 7, the via conductors 6 are used to connect the ground conductors 3 and 5 on both sides to suppress the higher-order propagation mode.

[0004]

However, in the coplanar guide transmission line of FIG. 7, the pitch between the via holes 6 (vertical direction in FIG. 7A) is limited due to manufacturing accuracy in the process of forming the via holes 6. Further, in a dielectric substrate as shown in FIG. 8 in which a plurality of coplanar guide transmission lines are arranged, the pitch between the transmission lines (left and right direction in FIG. 8) is limited by the arrangement of the via holes 6, and it is difficult to increase the density. Met.

Further, in the conventional coplanar guide transmission line, when the material and thickness of the dielectric substrate are constant, the characteristic impedance of the line is obtained by the width of the center conductor, the gap between the center conductor and the surface ground conductor, and the conductor thickness. The circuit is being designed by using a via hole, but the via hole is not taken into consideration. Actually, the distribution of the electromagnetic field varies depending on the presence or absence of via holes and the pitch of the via holes.
Strictly speaking, this means that the characteristic impedance is determined by full-wave analysis in a three-dimensional space in accordance with each case, especially in the high frequency region, and the design cost increases.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a transmission line in which characteristic deterioration due to reflection of signals at high frequencies and crosstalk is suppressed.

[0007]

The invention according to claim 1 is
A center conductor and surface ground conductors located on both sides of the center conductor are respectively formed on the surface of the dielectric substrate, a back surface ground conductor is formed on the back surface of the dielectric substrate, and the surface ground conductor and the back surface ground conductor are In a transmission line that is electrically conducting, forming a conductor wall that penetrates between the front and back surfaces of the dielectric substrate and extends in a direction along the extending direction of the central conductor,
A transmission line is characterized in that the front surface ground conductor and the back surface ground conductor are electrically connected by the conductor wall.

According to a second aspect of the present invention, a plurality of transmission lines according to the first aspect of the present invention are formed in parallel on the dielectric substrate.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In addition to the usual coplanar guide transmission line structure, the transmission line of the present invention has a conductor wall (ground plate) for connecting the ground conductors on the front and back surfaces of the substrate.
Is provided. This makes it possible to suppress the generation of higher-order electromagnetic waves and improve the deterioration of propagation characteristics due to reflection of signals at high frequencies and crosstalk.

[First Embodiment] FIG. 1 is a diagram showing a coplanar guide transmission line according to a first embodiment of the present invention.
(a) is a plan view and (b) is a bb sectional view of (a). In FIG. 1, 1 is a dielectric substrate, 2 is a central conductor as a signal line formed on the surface of the dielectric substrate 1, and 3 is a central conductor 2 thereof.
5 is a surface ground conductor formed on both sides of the back surface ground conductor formed on the back surface of the dielectric substrate 1, and 4 is a conductor wall (ground plate) for electrically connecting the surface ground conductor 3 and the back surface ground conductor 5. is there. The conductor wall 4 penetrates between the front and back of the dielectric substrate 1 and extends in the direction along the extending direction of the center conductor 2.

The substrate thickness of the dielectric substrate 1 is 0.15 mm, its relative permittivity is 4.7, and the line width of the central conductor 2 is 0.19 m.
m, the gap between the center conductor 2 and the surface ground conductor 3 is 0.1 mm, the conductor thickness of the center conductor 2, the surface ground conductor 3 and the back surface ground conductor 5 is 0.01 mm, and the thickness of the conductor wall 4 is 0. 1 mm, ground conductors 3 and 5 on both surfaces of the dielectric substrate 1
The conductor wall 4 and the conductor wall 4 were connected in an I shape, and the characteristic impedance was about 50Ω. In the present embodiment, the above conditions are used, but the structure in which the conductor wall 4 is moved to the left and right in FIGS. 1A and 1B without changing the other parameters (the surface ground conductor if necessary) It is also possible to adjust the characteristic impedance.

FIG. 2 is a S21 (transmission) characteristic of the S parameter as a result of numerical analysis of the structure of the coplanar guide transmission line having the structure of FIG. 1 and the structure of the conventional coplanar guide transmission line using the via hole described in FIG. Shows the frequency characteristics of. Here, the solid line is the case of the structure of the coplanar guide transmission line of the embodiment of FIG. The dotted line and the broken line show the case of the structure of the conventional coplanar guide transmission line using via holes in FIG. 7, and the results are 3 mm and 2 mm, respectively, between the via holes. Regarding the conventional coplanar guide transmission line, the dielectric substrate thickness, the relative permittivity, the conductor thickness and the gap have the same values as in the case of the present embodiment.
Regarding the line width of the center conductor, the characteristic impedance is 50
In order to make the value around Ω, it was set to 0.21 mm.

From the characteristics shown in FIG. 2, the structure of the present embodiment exhibits a good S21 characteristic, whereas the conventional structure has characteristic deterioration at a frequency corresponding to each via hole interval. Recognize.

In the conventional connection of the ground conductor between the front surface and the back surface by the via hole, the via hole interval of a half wavelength or less is required according to the operating frequency in order to suppress the unnecessary resonance mode. It is indispensable to make the via holes narrower and to form the via holes densely. However, this requires the manufacturing accuracy of the via holes and increases the manufacturing cost. Furthermore, since the sectional structure perpendicular to the signal propagation direction differs depending on the presence or absence of a via hole, it is difficult to calculate the characteristic impedance obtained by the sectional structure.

On the other hand, in this embodiment, since the conductor wall 4 for continuously connecting the surface grounding conductor 3 and the backside grounding conductor 5 of the dielectric substrate 1 in a plane shape is provided, the via hole is not necessary and the operating frequency is reduced. The change eliminates the need to change the via hole spacing. Furthermore, since the cross-sectional structure perpendicular to the signal propagation direction is uniform, the characteristic impedance is 2
It can be calculated only from the dimensional cross-sectional shape.

In the conventional coplanar guide transmission line, the characteristic impedance was found structurally by the substrate thickness, the center conductor line width, the gap between the center conductor and the surface ground conductor, and the center conductor thickness. In the form, the position of the conductor wall 4 is also a parameter that determines the characteristic impedance, so that the degree of freedom in design increases and
Transmission line characteristics covering a wide frequency band can be realized.

[Second Embodiment] FIGS. 3A and 3B are views showing a transmission line according to a second embodiment of the present invention, in which FIG. 3A is a plan view and FIG.
FIG. 6B is a sectional view taken along line bb of (a). The same components as those shown in FIG. 1 are designated by the same reference numerals. Here, the case where the number of the central conductors 2 is two, that is, the case where two transmission lines are parallelized is shown.

FIG. 4 is a diagram showing the S21 characteristic of the S parameter obtained by numerically analyzing the structure of the coplanar guide transmission line of FIG. 3 and the structure of the conventional coplanar guide transmission line shown in FIG. 8, and the solid line of FIG. The S21 characteristic of the structure, the broken line in FIG.
It is the S21 characteristic of the structure of. 5 is a diagram showing S11 (reflection characteristic), S31 (near end crosstalk characteristic), and S41 (far end crosstalk characteristic) of the transmission line having the structure of FIG. Further, FIG. 6 shows S1 of the transmission line of the conventional structure of FIG.
It is a characteristic showing 1, S31, and S41. Here, for the parameters such as the width of the center conductor, the gap between the center conductor and the surface ground conductor, and the substrate thickness, the values shown in the first embodiment are used
The width of the center surface grounded conductor 3'was 0.1 mm. Also, in the case of the conventional coplanar guide transmission line of FIG.
The distance between the via holes 6 (the vertical distance in FIG. 8A) is 3 m.
m.

From FIG. 4, as in the case of the transmission line having a single center conductor shown in FIG. 2, in the transmission line of the conventional structure shown in FIG. 8, characteristic deterioration due to the via hole spacing occurs near 24 GHz and 47 GHz. You can see that it is happening. Further, comparing FIG. 5 with FIG. 6, it can be seen that the characteristics of the structure according to the present invention (FIG. 5) show that the S1
While all of 1, S31, and S41 show good characteristics of -20 dB or less, in the characteristics of the conventional structure (Fig. 6), S11 exceeds -20 dB from around several GHz, and the overall characteristics are also It can be seen that it is deteriorated as compared with the present invention.

The transmission line of the present invention is not limited to the above-mentioned illustrated examples, and it goes without saying that various modifications can be made without departing from the scope of the present invention.

[0021]

As described above, according to the coplanar guide transmission line of the present invention, as compared with the conventional coplanar guide transmission line, the coplanar guide transmission line has a constant characteristic impedance over a wide band and between the center conductors. It is possible to achieve an excellent effect that the pitch can be narrowed to realize high-density wiring, and characteristic deterioration due to reflection of signals at high frequencies and crosstalk can be suppressed.

[Brief description of drawings]

1A and 1B are diagrams showing a coplanar guide transmission line having a single central conductor according to a first embodiment of the present invention, in which FIG. 1A is a plan view and FIG. 1B is a sectional view.

2 is an S-parameter S21 of the coplanar guide transmission line of FIG. 1 and the conventional coplanar guide transmission line of FIG.
It is a characteristic diagram which compared the characteristic.

3A and 3B are diagrams showing a coplanar guide transmission line having two central conductors according to a second embodiment of the present invention, where FIG. 3A is a plan view and FIG. 3B is a sectional view.

4 is an S-parameter S21 of the coplanar guide transmission line of FIG. 3 and the conventional coplanar guide transmission line of FIG.
It is a characteristic diagram which compared the characteristic.

5 is a characteristic diagram of S11, S31, and S41 characteristics of the S parameter of the coplanar guide transmission line of FIG.

6 is an S of the conventional coplanar guide transmission line of FIG.
It is a characteristic view of S11, S31, S41 characteristic of the parameter.

7A and 7B are views showing a conventional coplanar guide transmission line having one central conductor, in which FIG. 7A is a plan view and FIG. 7B is a sectional view.

8A and 8B are diagrams showing a conventional coplanar guide transmission line having two center conductors, FIG. 8A being a plan view and FIG. 8B being a sectional view.

[Explanation of symbols]

1: Dielectric substrate 2: Center conductor 3, 3 ': Grounded conductor 4: Conductor wall (ground plate) 5: Backside ground conductor 6: Beer hole

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yoshimitsu Arai             2-3-1, Otemachi, Chiyoda-ku, Tokyo             Inside Telegraph and Telephone Corporation F-term (reference) 5J014 CA00

Claims (2)

[Claims] 1. A center conductor and surface ground conductors located on both sides of the center conductor are respectively formed on a surface of a dielectric substrate, a back surface ground conductor is formed on a back surface of the dielectric substrate, and the surface ground conductor is In the transmission line in which the back-side ground conductor is electrically conducted, a conductor wall that penetrates between the front and back surfaces of the dielectric substrate and extends in a direction along the extension direction of the center conductor is formed, A transmission line, wherein a front-side ground conductor and the back-side ground conductor are electrically connected to each other. 2. A transmission line comprising a plurality of the transmission lines according to claim 1 formed in parallel on the dielectric substrate.